Diesel combustion may generate emissions, including particulate matter (PM). The particulate matter may include diesel soot and aerosols such as ash particulates, metallic abrasion particles, sulfates, and silicates. When released into the atmosphere, PM can take the form of individual particles or chain aggregates, with most in the invisible sub-micrometer range of 100 nanometers. Various technologies have been developed for identifying and filtering out exhaust PMs before the exhaust is released to the atmosphere.
As an example, soot sensors, also known as PM sensors, may be used in vehicles having internal combustion engines. A PM sensor may be located upstream and/or downstream of a diesel particulate filter (DPF), and may be used to sense PM loading on the filter and diagnose operation of the DPF. Typically, the PM sensor may sense a particulate matter or soot load based on a correlation between a measured change in electrical conductivity (or resistivity) between a pair of thin electrodes placed on a planar substrate surface of the sensor with the amount of PM deposited between the measuring electrodes. Specifically, the measured conductivity provides a measure of soot accumulation.
However, in such PM sensors, only a small fraction of the PM in the incoming exhaust gets collected across the electrodes formed on the surface of the sensor, thereby leading to low sensitivity of the sensors. Further, even the fraction of the PM that is accumulated on the surface may not be uniform due to a bias in flow distribution across the surface of the sensor. The non-uniform deposition of the PM on the sensor surface may further exacerbate the issue of low sensitivity of the sensor.
The inventors have recognized the above issues and identified an approach to at least partly address the issues. In one example, the issues above may be address by a particulate matter sensor comprising a pair of planar interdigitated electrodes spaced at a distance from each other and protruding from a surface of the PM sensor and a plurality of protruding flow guides located between the pair of planar interdigitated electrodes. Herein, the flow guides may include evenly spaced blocks arranged between pairs of tines of the interdigitated electrodes, spacing between the blocks being smaller than a distance between the pairs of tines of the pair of planar interdigitated electrodes. In this way, by including protruding electrodes and further including flow guides in between the electrodes, a single soot bridge may be divided into multiple soot bridges thereby increasing surface area coverage of the PM on the sensor surface and generating uniform distribution of the soot bridges on the sensor surface.
As one example, when a soot bridge formed between the electrodes encounters a flow guide, the soot bridge may branch out avoiding the block, and generating two pathways for the soot bridge to continue to form and grow. In this way, by branching the soot bridges at each of the flow guides, soot bridges may be able to grow across a larger surface area of the sensor, and may further generate a uniform distribution of soot on the sensor surface. Thus, by staggering the flow guides across the electrodes, soot bridges may be accumulated across multiple pathways and thereby, soot may be accumulated more uniformly across the sensor surface. Overall, these characteristics of the sensor may cause an output of the PM sensor to be more accurate, thereby increasing the accuracy of estimating particulate loading on a particulate filter.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.